There have been many proposals for devices that generate electricity from the motion of ocean waves for over a century. Devices generally attempt to convert ocean waves into motion that can be used to drive a turbine or linear motor to produce electricity, with the majority of devices falling into the former category. Some devices do not generate electricity directly, but convert the mechanical energy of ocean waves to another form of mechanical energy that can be used to do work.
Many problems confront the successful commercial exploitation of power from ocean waves.
The ocean is a difficult environment. The ocean tends to damage any exposed object, from those externally simple as ship hulls to moving propellers. Exposed moving parts are most susceptible to damage. This contributed to the early commercial failure, for example, of the Pelamis wave converter, which required constant, expensive maintenance. A lack of robustness makes practical power generation impossible.
Ocean waves are not regular and do not provide a constant motion. All power generators based on motion rely on the motion being constant in one direction for a period of time. Ocean waves change ‘direction’ with every single wave as it peaks and troughs. This is typically overcome by converting the mechanical potential energy in a wave into another type of energy (e.g. pumping water or turning a rotary turbine). Conversions of energy lead to inefficiencies.
Mooring is often a problem. Many devices use a fixed mooring or heavy weight as a ‘mechanical ground.’ A mooring that can withstand being so used is expensive and difficult to install, as well as being impractical in deeper waters; a separate ‘mechanical ground’ is expensive to transport and makes device service more expensive by restricting the mobility and accessibility of a device.
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